Coating compositions are well-known in the art and are used in a great variety of applications such as for primers, base coats and clear coats in vehicle original coatings and vehicle repair coatings. In this regard, great efforts have been made to develop coating compositions imparting the desired properties to the substrate or article to be coated. For example, coatings have been developed for e.g. protecting against abrasion, chemicals, corrosion, heat or mechanical impact. Furthermore, in vehicle repair coatings, there is an increasing demand in the market for fast drying coating compositions at room temperature.
In this regard, aspartate based coating compositions are well known in the art. For example, EP 0 403 921 describes coating compositions with binders based on a polyisocyanate component and an isocyanate-reactive component containing specific secondary polyamines. These secondary polyamines are also called polyaspartic acid derivatives and are based on reaction products of primary polyamines and diesters of maleic and/or fumaric acid. EP 0 470 461 also describes coating compositions for vehicle refinish applications containing a polyisocyanate component and an isocyanate-reactive secondary diamine prepared from 3,3′-dimethyl 4,4′-diamino dicyclohexylmethane and maleic diethylester. The isocyanate-reactive component further contains a hydroxyl-functional component consisting of polyhydroxypolyacrylates or mixtures of polyhydroxypolyacrylates and polyesterpolyols. WO 2005/073188 refers to aspartates which are prepared by first reacting a di- or polyamine with an unsaturated ester and then reacting the resultant product with a maleimide. U.S. Pat. No. 5,633,336 A refers to low-viscosity (cyclo)-aliphatic polyamines containing urea groups and having more than two amino groups that may be prepared by reacting (cyclo)aliphatic diamines with polyisocyanates containing isocyanurate groups or biuret groups. Such polyamines are useful as components in PUR reaction finishes and coating and adhesive compositions. WO 2013/098186 A1 refers to an aqueous urethane resin composition consisting mainly of the following (A) component and containing the following (B) and (C) components: (A) hydrophilic polyol, (B) water dispersible polyisocyanate, (C) aspartic acid ester having a secondary amino group. WO 2009/086026 discloses a transparent organic solvent-based clear coat coating composition comprising at least one binder with functional groups containing active hydrogen, in particular hydroxyl groups, at least one polyisocyanate cross-linking agent with free isocyanate groups and at least one epoxy-functional silane.
The above aspartate based coating compositions possess fast curing times. However, the balance of potlife of these coating compositions and early hardness development after application is not sufficient for certain applications, i.e. the viscosity of the compositions increases too rapidly after mixing the single components and prior to the application of the coating composition to a substrate. Furthermore, the mechanical and optical properties, such as adhesion and interlayer adhesion in a multi-layer structure, abrasion, chemical and corrosion resistance, yellowing in the pot and yellowing of the aspartate component on storage, of a coating obtained by applying and curing the coating composition on a substrate should be maintained on a high level.
Thus, the object of the present invention is to provide a coating composition having a well-balanced drying performance, i.e. fast curing times at a sufficient potlife, preferably a potlife of at least 30 min at room temperature, as well as a fast early hardness development, and in which the mechanical and optical properties, such as adhesion and interlayer adhesion in a multi-layer structure, abrasion, chemical and corrosion resistance, yellowing in the pot and yellowing of the aspartate component on storage, of the obtained coating are maintained on a high level.
In addition, other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.